/*
 * 
 * 
 * Copyright (C) Sivan Toledo, 2012
 * 
 * The CRC computation code is adapted from soundmodem, Copyright (C) 1999-2000
 * by Thomas Sailer (sailer@ife.ee.ethz.ch). That code is also released under GPL
 * version 2 or later.
 * 
 *      This program is free software; you can redistribute it and/or modify
 *      it under the terms of the GNU General Public License as published by
 *      the Free Software Foundation; either version 2 of the License, or
 *      (at your option) any later version.
 *
 *      This program is distributed in the hope that it will be useful,
 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *      GNU General Public License for more details.
 *
 *      You should have received a copy of the GNU General Public License
 *      along with this program; if not, write to the Free Software
 *      Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */


package sivantoledo.ax25;

//import java.util.Arrays;

public class Packet {
	
	private final int AX25_CRC_CORRECT   = 0xF0B8;
	private final int CRC_CCITT_INIT_VAL = 0xFFFF;
	private final int MAX_FRAME_SIZE = // not including delimiting flags
		                   7+7            // source and destination
		                  +(8*7)          // path
		                  +1+1            // control and PID
		                  +256            // information
		                  +2;             // frame checksum
	
	public static final int AX25_CONTROL_APRS                = 0x03;
	public static final int AX25_PROTOCOL_COMPRESSED_TCPIP   = 0x06;
	public static final int AX25_PROTOCOL_UNCOMPRESSED_TCPIP = 0x07;
	public static final int AX25_PROTOCOL_NO_LAYER_3         = 0xF0; // used for APRS

	private final int crc_ccitt_tab[] = {
	        0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
	        0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
	        0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
	        0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
	        0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
	        0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
	        0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
	        0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
	        0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
	        0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
	        0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
	        0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
	        0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
	        0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
	        0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
	        0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
	        0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
	        0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
	        0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
	        0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
	        0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
	        0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
	        0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
	        0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
	        0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
	        0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
	        0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
	        0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
	        0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
	        0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
	        0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
	        0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78,
	};

	private int crc = CRC_CCITT_INIT_VAL;
	private byte packet[] = new byte[MAX_FRAME_SIZE];
	private int size = 0;
	
	private float[] stats;
	public void statistics(float[] stats) { 
		this.stats = stats;
		for (float f : stats)
  		System.err.printf("%.2f ",f);
		System.err.println(format(Arrays.copyOf(packet, size-2)));
	}
	public float[] statistics() { return stats; }
	
	//public byte[] bytes()  { 
	//	return Arrays.copyOf(packet, size-2); // trim the checksum
	//}

	public byte[] bytesWithCRC()  { 
		return Arrays.copyOf(packet, size); // trim the checksum
	}

	public byte[] bytesWithoutCRC()  { 
		return Arrays.copyOf(packet, size-2); // trim the checksum
	}

	// this constructor is used by Afsk1200 to construct empty packets for reception
	public Packet() {
	}
	
	// this constructor is used for sending packets from raw bytes
	public Packet(byte[] bytes) {	
	  assert (crc == CRC_CCITT_INIT_VAL);
	  assert (bytes.length+2 <= packet.length);
	  
		for (int i=0; i<bytes.length; i++) {
			packet[size] = bytes[i];
			crc_ccitt_update(packet[size]);
			size++;
		}
		
	  int crcl = (crc & 0xff) ^ 0xff;
	  int crch = (crc >> 8) ^ 0xff;

	  packet[size] = (byte) crcl;
		crc_ccitt_update(packet[size]);
		size++;

	  packet[size] = (byte) crch;
		crc_ccitt_update(packet[size]);
		size++;
		
		assert (crc == AX25_CRC_CORRECT);
	}
	
	public Packet(String destination,
			          String source,
			          String[] path,
			          int      control,
			          int      protocol,
			          byte[]   payload) {
		int n = 7 + 7 + 7*path.length + 2 + payload.length;
		byte[] bytes = new byte[n];
		
		int offset = 0;
		
		addCall(bytes, offset, destination, false);
		offset += 7;
		addCall(bytes, offset, source     , path==null || path.length==0);
		offset += 7;
		for (int i=0; i<path.length; i++) {
			addCall(bytes, offset, path[i], i==path.length-1);
			offset += 7;
		}
		
		bytes[offset++] = (byte) control;
		//System.out.printf("control = %02x\n", bytes[offset-1]);
		bytes[offset++] = (byte) protocol;
		//System.out.printf("protocol = %02x\n", bytes[offset-1]);
		
		for (int j=0; j<payload.length; j++) {
			bytes[offset++] = payload[j];
			//System.out.printf("data = %02x\n", bytes[offset-1]);
		}
		
		assert(offset == n);
		assert(size == 0);

	  assert (crc == CRC_CCITT_INIT_VAL);
	  assert (bytes.length+2 <= packet.length);
	  
		for (int i=0; i<bytes.length; i++) {
			packet[size] = bytes[i];
			crc_ccitt_update(packet[size]);
			size++;
		}
		
	  int crcl = (crc & 0xff) ^ 0xff;
	  int crch = (crc >> 8) ^ 0xff;

	  packet[size] = (byte) crcl;
		crc_ccitt_update(packet[size]);
		size++;

	  packet[size] = (byte) crch;
		crc_ccitt_update(packet[size]);
		size++;
		
		assert (crc == AX25_CRC_CORRECT);
	}

	static void addCall(byte[] bytes, int offset, String call, boolean last) {
	  int i;
	  boolean call_ended = false;
	  char c = ' ';
	  int ssid = 0;

	  for (i=0; i<6; i++) {
	    if (i<call.length())
	    	c = call.charAt(i);
	    else
	    	call_ended = true;
	    if (call_ended || !Character.isLetterOrDigit(c) || c=='-') {
	    	call_ended = true;
	    	c = ' ';
	    } else c = Character.toUpperCase(c);
	    bytes[offset++] = (byte) (c << 1);
	  }

	  for (i=0; i<call.length(); i++) { 
	    c = call.charAt(i);
	    if (c=='-' && i+1<call.length()) {
	    	ssid = Integer.parseInt(call.substring(i+1));
	      if (ssid > 15 || ssid < 0) ssid=0; // this is an error
	      break;
	    }
	  }

	  /* The low-order bit of last call SSID should be set to 1 */
	  ssid = (ssid << 1) | (0x60) | (last ? 0x01 : 0);
    bytes[offset++] = (byte) ssid;
	}
	
	/*** Packet parser ***/
	
	public String source, destination;
	public String[] path;
	public byte[]   payload;
	
	private static String parseCall(byte[] packet, int offset) {
		String call = "";
		int c, i;
		//int size = 0;
		
		for (i=0; i<6; i++) {
			c = (packet[offset+i] > 0) ? packet[offset+i] >> 1 : (packet[offset+i]+256) >> 1;
			//System.out.printf("Parsing byte %02x offset %d <%c>\n",c,offset+i,(char)c);
			if ((char) c != ' ')
				call += (char) c;
		}
		
		c = (packet[offset+i] > 0) ? packet[offset+i] >> 1 : (packet[offset+i]+256) >> 1;	
		int ssid = c & 0x0f;
	  if (ssid != 0)
	  	call += String.format("-%d", ssid);
		
		return new String(call);
	}
	
	public void parse() {
		int offset= 0;
		destination = parseCall(packet,offset);
		offset += 7;
		source      = parseCall(packet,offset);
		offset += 7;
		
		int repeaters = 0;
		while (offset+7 <= size && (packet[offset-1] & 0x01) == 0) {
			repeaters++;
			if (repeaters > 8) break; // missing LSB=1 to terminate the path
			String path_element = parseCall(packet,offset);
			offset += 7;
			if (path == null) {
				path = new String[1];
				path[0] = path_element;
			} else {
				path = Arrays.copyOf(path,path.length+1);
				path[path.length-1] = path_element;
			}
		}
		
		offset += 2; // skip PID, control
		//System.out.println("copying packet from "+offset+" to "+(size-2));
		payload = Arrays.copyOfRange(packet, offset, size - 2); // chop off CRC
	}
	
	
	public static String format(byte[] packet) {
		String   source,destination;
		String[] path = null;
		byte[]   payload;
		int offset= 0;
		int repeaters = 0;
		int size = packet.length;
		
		destination = parseCall(packet,offset);
		offset += 7;
		source = parseCall(packet,offset);
		offset += 7;
		
		while (offset+7 <= size && (packet[offset-1] & 0x01) == 0) {
			repeaters++;
			if (repeaters > 8) break; // missing LSB=1 to terminate the path
			String path_element = parseCall(packet,offset);
			offset += 7;
			if (path == null) {
				path = new String[1];
				path[0] = path_element;
			} else {
				path = Arrays.copyOf(path,path.length+1);
				path[path.length-1] = path_element;
			}
		}
		
		offset += 2; // skip PID, control
		//System.out.println("copying packet from "+offset+" to "+(size-2));
		payload = Arrays.copyOfRange(packet, offset, size); 
		
		
		StringBuilder builder = new StringBuilder();
		builder.append("[");
		
		builder.append(source);
		builder.append('>');
		builder.append(destination);
		if (path!=null) for (String via: path) {
			builder.append(',');
			builder.append(via);
		}
		builder.append(':');
		
		for (int i=0; i<payload.length; i++) {
			char c = (char) payload[i];
			if (c >= 0x20 && c <= 0x7E) builder.append(c);
			else builder.append(String.format("\\x%02x",payload[i]));
		}
		/*
		for (int i=0; i<size; i++) {
			char c = (char) packet[i];
			if (c >= 0x20 && c <= 0x7E) builder.append(c);
			else builder.append('.');
		}
		//builder.append(Arrays.toString(packet));
		 */
		builder.append("]");
		return builder.toString();

	}
	
	private void crc_ccitt_update(byte b) {
    crc = (crc >> 8) ^ crc_ccitt_tab[(crc ^ b) & 0xff];
  }

	public boolean addByte(byte b) {
		//char c = (char) b;
		//System.out.printf("%c %c %02x\n",b,b>>1,(byte)c);
		
		if (size >= MAX_FRAME_SIZE) return false;
		
		crc_ccitt_update(b);
		
		packet[size] = b;
		size++;
		
		return true;
		//System.out.printf("j %02x %08x\n",b,crc);
	}
	
	public boolean terminate() {
		//System.out.printf("checking termination last byte %02x\n",packet[size-1]);
		if (size < 18) return false; // at least source, destination, control, pid, FCS.
		if (crc == AX25_CRC_CORRECT) {
			//System.out.println("CRC Correct!\n");
			return true;
		} else
			return false;
	}

	@Override
	public String toString() {
		parse();
		StringBuilder builder = new StringBuilder();
		builder.append("[");
		
		builder.append(source);
		builder.append('>');
		builder.append(destination);
		if (path!=null) for (String via: path) {
			builder.append(',');
			builder.append(via);
		}
		builder.append(':');
		
		for (int i=0; i<payload.length; i++) {
			char c = (char) payload[i];
			if (c >= 0x20 && c <= 0x7E) builder.append(c);
			else builder.append(String.format("\\x%02x",payload[i]));
		}
		/*
		for (int i=0; i<size; i++) {
			char c = (char) packet[i];
			if (c >= 0x20 && c <= 0x7E) builder.append(c);
			else builder.append('.');
		}
		//builder.append(Arrays.toString(packet));
		 */
		builder.append("]");
		return builder.toString();
	}	
}
